The present invention relates to a releasable lock mechanism for the service brakes of a vehicle and more particularly relates to such a mechanism which represents an improvement over that disclosed in U.S. Pat. No. 3,757,604 issued on Sept. 11, 1973 to Kenneth Roger Schroeder and assigned to Deere & Company, as is the present application.
The above-identified patented lock mechanism includes a hand-operated actuator rod which is biased toward a pawl-deactivating position wherein it acts against a pawl which is biased toward a pedal-lock position, the bias acting on the rod being large enough to override that acting on the pawl. The rod may be movable to a detented pawl-releasing position wherein the counter biasing force is removed from the pawl prior to or after movement of a brake pedal to a brake-engage position. In the first case the biasing force acting on the locking pawl moves the latter against the brake pedal and when the brake pedal is subsequently moved to its brake-engage position the pawl moves to a pedal-lock position and in the second case, the locking pawl moves immediately to its pedal-lock position. The pawl is released from its pedal-lock position so as to release the brake pedal by releasing the actuator rod from its detented pawl-activating position, whereupon the biasing force acting thereon is again transferred to the pawl such that upon the brake pedal being overtraveled slightly beyond its brake-engage position the pawl will be released to return to its pedal-release position.
The patented lock mechanism has the disadvantage that the operator's hand as well as his foot is required to operate it. Thus, the operator must often interrupt operation of hand levers for controlling other functions of the vehicle in order to effect locking of the service brakes.